PARENT SESSION
Poster Session #16: Fire Ecology.
Tuesday, August 7, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Shrub encroachment in a protected palm savanna. Responses to fire in three dominant Asteraceae species.

Galindez, Guadalupe¹, Pereyra, Cristian¹, Ferro, Ezequiel¹, Scopel, Ana¹, ¹

ABSTRACT- In the El Palmar National Park, a temperate palm savanna of eastern Argentina, we have documented a massive increase in the abundance of a group of native shrubs known as "chilcas", particularly Baccharis dracunculifolia, B. medulosa and Eupatorium buniifolium (Asteraceae), after the implementation of new management practices that involved exclusion of livestock grazing and altered fire regime. The three species occur together in most sites, but B. dracunculifolia is preferentially associated with recent fire events. The aim of this work was to study the response of these species to fire. We estimated several demographic parameters at a recently burned site and at an adjacent, control site that has not been burned for at least 4 years. Fire induced profuse sprouting from underground reserve structures in both E. buniifolium and B. medulosa. In B. medulosa all sprouting shoots flowered and produced abundant seeds, which readily germinated in the field. Seed production per plant did not differ between sites. In B. dracunculifolia regeneration after fire depended exclusively on the promotion of seedling emergence at the burned site, which was four times higher than in the unburned area. Hence, E. buniifolium and B. medulosa may be regarded as fire-resistant and B. dracunculifolia as seed-dependent. The different life history strategies exhibited by the three species may help to explain the observed population patterns at sites with contrasting fire histories.

KEY WORDS: Asteraceae, fire , sprouting, seedling